1. Field of the Invention
The present invention relates to downhole pumps. More particularly, the present invention relates to rod-type pumps in which a plunger is used so as to draw fluids through a standing valve and pass the fluids through a traveling valve so as to form a fluid column within the production tubing. More particularly, the present invention relates to downhole pumps in which the traveling valve is controlled during the movement of the plunger so as to facilitate the equalization of pressures within the production tubing while, at the same time, effectively removing sand accumulations from within the production tubing, within the barrel, and within the plunger.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Artificial lift refers to the use of an artificial means to increase the flow of fluids, such as crude oil, gas or water, from a production well. Generally, this is achieved by the use of a mechanical device inside the well (known as a pump) or by decreasing the weight of the hydrostatic column by injecting gas into the liquid some distance down the well. Artificial lift is needed in wells when there is insufficient pressure in the reservoir to lift the produce fluids to the surface, but often is used in naturally flowing wells to increase the flow rate above what would flow naturally. The produced fluid can be oil, water, or a mix of oil and water, along with produced fluids having some amount of gas.
Conventional oil and gas wells include a cased wellbore with a tubing string extending down to the hydrocarbon bearing formation. The casing is perforated at the production level to permit the hydrocarbons to flow into the casing and the bottom of the tubing is generally open to permit the hydrocarbons to flow into the tubing and up to the surface. Oftentimes, there is insufficient pressure in a formation to cause oil and other liquids and gases to readily flow to the surface. It therefore becomes necessary to install the artificial lift system so as to pump the fluids to the surface.
One of the most common types of artificial lift systems is a rod pump. This type of pump is positioned in the well at the level of the fluids to be removed and is mechanically driven by a series of rods connecting the pump to a pumping unit at the surface. These rod pumps include the simple combination of a cylinder or barrel with a piston or plunger and a suitable intake valve and a discharge valve. The intake valve is often referred to as a “standing valve” and the discharge valve is often referred to as a “traveling valve”.
Two of the more common types of rod pumps are the tubing pump in which the pump barrel is attached directly to the tubing and is lowered to the bottom of the well as the tubing is run into the well. The plunger is attached to the bottom of the sucker rod that is positioned within the pump barrel. The intake valve is positioned at the bottom of the pump barrel and the traveling valve is positioned on the plunger. The second type of pump is often referred to as an insert pump and the entire assembly is attached to the bottom of the sucker rod. The barrel is held in place by special seating nipple or other device positioned within the tubing. This type of pump has the advantage that it can more easily be removed for repair or replacement than a tubing pump.
The operation of a rod pump is relatively simple. The plunger reciprocates up-and-down in the barrel under the force of the sucker rod. During the upstroke, the traveling valve is closed and the fluid above the plunger is lifted to the surface by the plunger and the sucker rod. At the same time, the standing valve is open so as to allow fluids to flow into and fill the now-evacuated barrel. On the downstroke, the standing valve is closed so as to trap the fluids in the barrel. The traveling valve is opened allowing the compressed fluids to flow through the plunger so that they can be lifted during the subsequent cycle.
While rod pumps have been in use for decades and have proven to be economical and reliable, they still experience certain shortcomings and problems. Some of these problems are associated with valves which are generally of the ball-and-seat variety. This type of valve is opened and closed by pressure differentials across the valve.
One problem that is often encountered is referred to as gas lock. This occurs when there is a substantial amount of gas that flows into the pump with the liquid. Because of the high compressibility of the gas, insufficient pressure is generated during the downstroke of the pump to open the traveling valve against the hydrostatic pressure of the fluid in the production tubing. Accordingly, the pump can repeatedly cycle without any fluid being lifted to the surface.
Fluid pound is another problem that is often encountered. If the barrel is only partially filled with liquid, the plunger forcefully encounters the liquid level part way through the downstroke so as to cause severe stress to be placed on the pump. Pump-off damage often occurs when the barrel is not completely filled with fluid. Damage occurs in the wall of the working barrel due to overheating of the pump which is caused by the absence of fluid to carry away the heat carried by friction in the pump. Additionally, fluid pound can cause a whipping action of the sucker rod so as to cause potential damage to the production tubing and damage to the sucker rod.
During the production of the formation fluid, mineral particles, often referred to as sand, may be swept into the flow path. The sand may erode production components, such as the downhole pump or sucker rod pump, the control valves on the surface, the ball-and-seat arrangement of the standing valve, etc. in the flow path. When substantial quantities of sand are carried along as oil and/or gas is removed from a formation, the sand can eventually plug the openings in the interior of the tubing by which the hydrocarbon production is withdrawn to the earth's surface. It is not uncommon for the pump itself to stick and/or the barrel to stick as a result of sand or other particulate matter becoming caught between the barrel and the plunger. The tolerances between the barrel and the plunger are close so as to effect a seal between the plunger and the barrel. If sand lodges therebetween, either the plunger or the barrel will be cut or the plunger sticks in the barrel. The structure of such pumps makes them particularly prone to such damage because such pumps rely on a seal which is formed between the plunger and barrel by the leading edge of the plunger.
Generally, when the pump becomes “sanded in” in the production tubing, a very complicated procedure is required so as to remove the sanded-in components of the well. Typically, the production tubing would have to be removed so as to separate the pump from the tubing and remove the sand accumulation. As such, is important that sand the removed from the interior of the production tubing and from the interior of the barrel so as to prevent these problems from occurring.
Typically, such rod pumps do not operate at very well in association with multi-phase fluids are with gas wells. In multi-phase fluids, there can be a gas and a liquid, such as oil or water. In gas wells, typically, the multi-phase liquid will include gas, water and light oil. Because of the high percentage of gas in such wells, the problems associated with gas locks and/or liquid pounding occur more frequently.
Currently, there is a strong trend toward horizontal or deviated wells. Such rod pumps are not particularly effective in pumping the fluid in such deviated or horizontal wells. This is because the sucker rod will have to travel in a similar pattern to that of the deviated wells. In certain circumstances, the deviated well can have a convoluted or S-shaped configuration. As such, it is very difficult for the rod to effectively reciprocate upwardly and downwardly in such deviated wells. Furthermore, when sucker rods are used in such deviated wells, they can rub against the side of the production tubing so as to eventually perforate the production tubing in areas that are not desired. The frictional contact between the rod in the inner wall of the production tubing can further potentially damage the sucker rod such that the well will need to be repaired by pulling the production tubing and replacing the damaged tubing or by pulling the sucker rod and replacing the damaged section of the sucker rod. Once again, this could lead to an extended period of non-productivity of the well.
In the past, a variety of patents have issued relating to such rod pumps. In particular, U.S. Pat. No. 2,344,786, issued on Mar. 21, 1944 to Patterson et al., describes an anti-pound pump pressure equalizer. This anti-pound pump has a working chamber between the standing and traveling valves. A means is exposed at one side to the working chamber pressure and is yieldable in one direction in accordance with rising pressure in the working chamber during each discharge stroke of the pump. A chamber is formed that is isolated from the rising pressure. The yielding means is positionable during the course of the yielding movement for opening the working chamber of the pump into pressure-equalizing communication with the production column independent of the traveling valve of the pump. A means is provided for returning the yieldable means to an interactive position subsequent to pressure equalization.
U.S. Pat. No. 4,599,051, issued on Jul. 8, 1986 to H. L. Spears, discloses a traveling valve assembly for a fluid pump. This traveling valve assembly includes a ball valve actuator which engages the ball valve during the downstroke of the sucker rod to force the ball open into an open fluid transmitting relationship with respect to the valve seat.
U.S. Pat. No. 4,691,735, issued on Sep. 8, 1987 to J. B. Horton, shows a plunger valve apparatus for an oil well pump. The traveling valve or standing valve for the pump includes a piston which lifts the ball above the valve seat to open the valve and sets the ball back on to the seat to close the valve. The ball is contained within a ball protection shield which prevents uncontrolled movement by the ball inside a middle tube. The piston has openings and the ball protection shield has apertures which allow fluid to flow through the valve without engaging the ball.
U.S. Pat. No. 4,708,597, issued on Nov. 24, 1987 to A. V. Fekete, describes a plunger with a simple retention valve. The fluid pump has a plunger reciprocating within a working cylinder and a standing intake retention valve. The plunger includes a stem having a plug and a stop affixed to it. The plunger also has a body that is slidably engaged to the cylinder and located on the discharge side of the plug and on the intake side of the stop. Upon the upstroke of the plunger, a plug surface engages with a sealed body and therefore pumps the fluid before it. Meanwhile, fluid flows in behind the plunger through the standing intake retention valve. On the downstroke, the plug disengages from the body so as to allow fluid to flow noncompressibly past the plunger.
U.S. Pat. No. 4,741,679, issued on May 3, 1988 to D. L. Blassingame, discloses an oil well traveling valve for a sucker rod-operated oil pump. This traveling valve includes a fluid outlet ported pump head connecting inner and outer sleeves with the upper end of a working barrel for reciprocating the working barrel. A valve is tethered within the inner sleeve in a manner ensuring separation of the valve from its seat for opening the pump fluid passageway and exhausting gas from the pump bore with each complete sucker rod stroke.
U.S. Pat. No. 4,781,543, issued on Nov. 1, 1988 to G. M. Sommer, teaches an artificial lift system for oil wells in which oil is recovered from an underground formation more efficiently by the use of a subsurface power piston that reciprocates a subsurface pump. A series of connecting rods connects the power piston to the subsurface pump. The subsurface power piston is driven upwardly by a surface-mounted hydraulic actuation system. The distance between the subsurface pump and the power piston is set so that pressure at the depths of the power piston and pump closely counterbalance the weight of the sucker rod string at all positions of the stroke with a slight down bias.
U.S. Pat. No. 4,781,547, issued on Nov. 1, 1988 to R. D. Madden, shows a gas equalizer for a downhole pump. This gas equalizer device is intended to avoid the fluid pounding condition. The gas equalizer device includes a pushrod having a marginal end reciprocatingly enclosed in a slidable manner within a housing which is mounted to the usual traveling valve cage of the downhole pump. The push rod is alternately moved from an extended to a retracted position each upstroke and downstroke of the pump. The free terminal end of the push rod is arranged to engage the ball check valve of the traveling valve assembly as the pump commences the downstroke. This unseats the ball so as to allow any accumulated gases to escape from the variable pump chamber. The escape gases flow out of the pump and up the tubing string along with the produced fluid.
U.S. Pat. No. 4,867,242, issued on Sep. 19, 1989 to G. E. Hart, discloses a method and apparatus for breaking a gas lock in an oil well pump. This apparatus includes a stationary barrel with a standing valve on the bottom, a reciprocating piston in the barrel with a traveling valve on the bottom of the piston, and an unseating rod positioned above the standing valve and adapted to protrude into the traveling valve to unseat the ball closure thereof near the bottom extremity of the downstroke of the piston.
U.S. Pat. No. 4,907,953, issued on Mar. 13, 1992 Hebert et al., teaches a locking gas equalizer for use with a subsurface pump for lifting fluids having a high gas content. A mechanical lifting piston and rod are slidably mounted beneath the check valve in the traveling pump assembly. When the pump reaches the bottom of its downstroke, the piston raises the rod and unseats the check valve. As the pump cycle reverses at the top of the stroke, the inertia of the piston also causes the rod to be raised for unseating the check valve and allowing a small amount of fluid to drop into the pump chamber. As a result, gas pressure within the pump chamber volume is positively equalized to prevent gas lock of the pumping action.
U.S. Pat. No. 5,407,333, issued on Apr. 18, 1995 to C. T. Lambright, discloses a rod-driven downhole pump. The pump includes a traveling barrel contained within a pump housing, a central pump rod extending axially within the barrel, a valve ball located at the lower end of the pump rod, and a valve seat near the barrel lower end. The pump rod includes a rod shoulder for engaging the upper end of the barrel. The barrel contains annular passageways for the flow of fluid through the barrel. The pump rod is reciprocable within the barrel and the barrel is reciprocable within the pump housing. The downward stroke of the pump rod causes the rod shoulder to engage the barrel's upper end and concurrently displaces the ball valve below the valve seat so as to allow environmental fluid to flow through the annular passageways of the barrel. On the upstroke of the pump rod, the valve ball engages the valve seat and pushes the pump barrel upwardly within the pump housing.
U.S. Pat. No. 5,139,398, issued on Aug. 18, 1992 to T. R. Downing, provides a neutralizer valve for a downhole pump. This neutralizer valve is for use in conjunction with one or more reciprocating pumps. The neutralizer valve takes the place of a regular traveling valve and a rod pump. The neutralizer valve includes a drag plunger for passing a crude and natural gas mix therethrough on a downstroke of the tubing string. The neutralizer valve includes a guide barrel that is connected into the rod pump plunger and contains a ported seal stem that is arranged to move up-and-down therein. The ported seal stem includes a keyed rod at its upper end that is to travel up-and-down in a keyway that is formed through a ported disc which is arranged across the guide barrel interior. On an up-stroke of the rod tubing string, the valve closes so as to create a void between it and a standing valve of a downhole pump. On the downstroke, the stem collar valve face is moved off the seat so as to open the valve to allow a fluid to flow therethrough.
U.S. Pat. No. 5,141,411, issued on Aug. 25, 1992 to J. H. Klaeger, discloses a center-anchored rod-actuated pump which is particularly useful in deep and/or low-pressure stripper wells. The pump includes a traveling valve and a standing valve. The traveling valve is provided with a valve member which includes a downwardly extending stem which terminates in a lower bearing surface. The standing valve is provided with a valve member having an upper bearing surface. As the plunger of the pump is reciprocated, the lower bearing surface of the valve member of the traveling valve mounted therein contacts the upper bearing surface of the valve member of the standing valve when the plunger is near the maximum extent of downward travel so as to force the traveling valve open and/or force the standing valve closed depending upon fluid pressure conditions and whether the standing valve is stuck open.
U.S. Pat. No. 5,628,624, issued on May 13, 1997 to J. A. Nelson, discloses an assembly for unseating a seated traveling valve ball. The assembly includes a tubular member having therein a piston with an actuator for engaging the ball. Mechanical advantage is provided either by providing a sealing area of the piston that is greater than the sealing area of the seat valve and/or by providing an engaging member suitable to strike the seated ball asymmetrically with respect to the vertical axis through the center line of the ball.
U.S. Pat. No. 5,829,952, issued on Nov. 3, 1998 to D. W. Shadden, provides a reversible valve ball assembly for use in a downhole pump check valve. The reversible valve ball can be removed, inverted and reinserted into the check valve to provide a new valve ball sealing surface. The reversal of the valve ball is performed after the original valve ball sealing surface has worn and deteriorated so that it can no longer seat properly to form a seal between the valve ball surface and a valve seat. A set of irregularly-shaped valve ball guide arms are provided which rotate within valve guide apertures to provide a clean action between the valve guide apertures and the valve ball arms to prevent accumulation of debris. An elongated gas-breaker fin is provided so as to prevent a gas lock. The gas-breaker fin enables a reduced vertical length for the valve ball arms so that a reversible symmetric valve ball assembly can be utilized.
U.S. Pat. No. 6,481,987, issued on Nov. 19, 2002 to M. B. Ford, discloses an improved traveling valve that has a valve positioned on a seal stem so that the ball is reliably centered when seated on the valve seat. The traveling valve is constructed so that a lower portion of the valve rotates during pumping so as to impart rotational movement of the fluid passing therethrough. The rotational movement is caused by angled channels in an interior portion of a vane and the rotator positioned at the bottom of the traveling valve so as to work in combination with the angled channels in the seal stem.
U.S. Pat. No. 7,051,813, issued on May 30, 2006 to Hayes et al., shows a pass-through valve and stab tool. This tool allows periodic access through one or more one-way of valves installed in a fluid flow stream. Fluid can flow through the bypassed valves or through the tools used to bypass the valves in the manner of a reciprocating production pump. A stab tool cooperates with a valve to unseat a ball from a ball seat so as to bypass the ball and pass through the ball seat. The stab tool is conveyed by tubing for discharge of fluid through ports in the stab tool. A rod is installed within a pump between a reciprocating uphole valve and a downhole valve is arranged so that when the pump is closed, the stab tool at the rod's lower and passes through the downhole valve and a projection at the rod's upper end passes through the uphole valve such that the pump is partially closed.
U.S. Pat. No. 7,878,767, issued on Feb. 1, 2011 to M. B. Ford, describes a cyclonic debris-removing valve. The ball valve is capable of transitioning between an open position and a closed position. The ball valve includes a hydraulic piston, a containment union, a ported stem, a containment cage, and a drag plunger. The ball valve is adapted to regulate the flow of fluid northward through the valve. During a pump downstroke, fluid enters the drag plunger, moves northward through the containment cage and into the interior of the ported stem, exits the interior of the ported stem and enters a plurality of angled vanes so as to impart cyclonic motion on fluid passing northward therethrough so as to assist in the removal of debris. During the downstroke, a pedestal portion of the hydraulic piston unseats the ball from the seat.
U.S. Patent Application Publication No. 2005/0053503, published a Mar. 10, 2005 to R. D. Gallant, describes an anti-gas-lock pumping system. The pump is designed such that any gas present in the fluid that is pumped is completely displaced from the pumping chamber with each downstroke of a pump plunger.
U.S. Patent Application Publication No. 2013/0025846, published on Jan. 31, 2013 to G. Scott, teaches an apparatus for use with the traveling valve assembly of a downhole pump for releasing gas and so as to prevent gas locks. The apparatus comprises a piston slidably disposed within a cylindrical housing. The piston is driven by an attached plunger element. On the downstroke of the pump, the piston protrudes through an end of the cylindrical housing so as to engage and open the adjacent valve. On the upstroke of the pump, the piston retracts into the cylindrical housing so as to disengage from the valve and to allow the valve to close. Fluid flows along the outer surface of the apparatus by means of fluid ports connected by defined fluid passages.
U.S. Pat. No. Re 33,136, reissued on Feb. 13, 1990 R. D. Madden, describes a gas equalizer device for use in conjunction with a reciprocating pump located downhole within a wellbore. The gas equalizer device includes a pushrod having a marginal end reciprocatingly enclosed in a slidable manner within a housing which is mounted to the usual traveling valve cage of the downhole pump. The push rod is alternately moved from an extended position to a retracted position on each upstroke and each downstroke of the pump. The free terminal end of the pushrod is arranged to engage the ball check valve of the traveling valve assembly as the pump commences the downstroke. This unseats the ball so as to allow any accumulated gases to escape from the variable pump chamber.
It is an object of the present invention provide a downhole pump system with higher system efficiencies.
It is another object of the present invention to provide a downhole pump system that has greater operational capabilities.
It is another object of the present invention to provide a downhole pump system that has lower operating costs.
It is still another object of the present invention to provide a downhole pump system that maximizes hydrocarbon production.
It is another object of the present invention to provide a downhole pump system that avoids gas locks.
It is a further object of the present invention to provide a downhole pump system that operates in horizontal and/or highly-deviated production tubing.
It is another object of the present invention to provide a downhole pump system that is able to able to produce at low rates and at high pressures.
It is another object of the present invention to provide a downhole pump system that is operable at extended depths and high temperatures.
It is still another object of the present invention to provide a downhole pump system that effectively remove solids from the fluid during the production.
It is another object of the present invention provide a downhole pump system that provides extended runtime.
It is still a further object of the present invention to provide a downhole pump system that has reduced sensitivity to solids plugging.
It is another object of the present invention to provide a downhole pump system that reduces rod buckling stress and reduces the problems associated with deviated rods.
It is still another object of the present invention to provide a downhole pump system that maximizes pump fillage.
It is still another object of the present invention provide a downhole pump system that avoids ball dance damage.
It is still a further object of the present invention to provide a downhole pump system that minimizes fluid pound and the problems resulting from fluid pound.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.